A critical comparison of computed and experimental pressure distributions and force coefficients on a blunted-cone at angle of attack

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Virginia Tech

Comparisons have been made between a general three-dimensional characteristics solution and available experimenta1 data with regard to the pressure distributions and force and moment coefficients for a spherically-capped 9-degree semivertex angle circular cone, up to angles of attack of 20 degrees. Also, predictions were computed using modified Newtonian theory since this theory has been widely used for bodies flying at hypersonic speeds. Several significant results have been found fran these comparisons. These are briefly summarized in the following statements: 1. The GASL program is adequate to the task of predicting the inviscid pressure distribution and the resultant aerodynamic forces for bodies at angle of attack. 2.The irregularities that occur in the GASL solution on the leeward side of a body at large angle of attack may limit its applicability in its present form to small angles of attack. For the blunt cone body considered here it appears that a 10-degree angle of attack would be an upper limit of applicability. 3. The GASL program represents a new capability which can be employed to begin a more rigorous analysis of the viscous effects which are known to be prevalent in the hypersonic speed range. 4. Only under very special conditions is modified Newtonian theory useful. Inasmuch as these conditions are defined in only general terms, no reasonable range of applicability can be stated. In those cases where it is employed, reliability remains to be proven, In the present application the method was shown to be unreliable. 5. The GASL program represents a first step towards the ability to compute the supersonic inviscid flow field about bodies at angle of attack, both for the study of inviscid and viscous flow fields. However, if progress is to be made towards a complete understanding of these flow fields, the problems revealed in the present comparisons would indicate that much more research and analysis is required.